ACHRNEWS

Using Thermal Energy Storage To Dodge The Energy Crisis

October 31, 2001
LOS ANGELES, CA — In 1990, construction began on 801 Towers, a 24-story, 430,000-sq-ft office building in downtown Los Angeles. The building was designed to include 8,300-ton-hrs of thermal energy storage (TES) to shift peak loads in order to qualify for incentives and off-peak rates offered by the Los Angeles Department of Water and Power (LADWP). The system is capable of approximately 11,000-ton-hrs of capacity, according to Victor Ott, president of Cryogel in San Diego, CA.

Flack and Kurtz of San Francisco, the principal engineer, and LADWP may not have foreseen the energy crisis coming, but in hindsight, the system has proven to be a prime example of engineering foresight, says Ott.

The engineer, building owner, and local utility designed the system with the flexibility to deal with uncertainties in electrical supplies that are now exacerbated by deregulation of electricity markets. Ott says the LADWP’s incentives and off-peak rates were part of an overall business plan that has shielded customers in that areas from many of the problems faced today by ratepayers elsewhere in California. Energy supply uncertainties and the need for design foresight have become the norm in California, says Ott.

801 TOWERS DURING CONSTRUCTION

Ott says that after incentive payments from the LADWP, the system cost was approximately $640,000 more than a non-storage air conditioning system. The system is capable of shifting approximately 2,000 kW of electrical demand to off-peak periods, according to Ott. The net installed cost was approximately $58/ton-hr of actual thermal storage capacity.

THE STORAGE TANK

The system includes a 180,000-gal concrete tank with a polyethylene liner, approximately 750,000 spherical ice containers, and two 700-ton, Trane, three-stage centrifugal chillers. The tank is located three levels below the street and adjacent to the underground parking garage. The roof of the concrete tank is formed by a ramp that connects two garage levels. As with most civic centers, parking is a premium in downtown L.A., and this tank configuration and ice storage technology was chosen to save space in the parking garage, says Ott.

The concrete tank was fitted with a 1/8-in.polyethylene liner to prevent leaks in the underground concrete tank from normal thermal expansion and contraction. The design provides 1 1/2 in. of Styrofoam board insulation between the liner and the internal tank wall offering double-wall leak security as well as a vapor barrier for the insulation, says Ott.

For more information, contact Cryogel, P.O. Box 910525, San Diego, CA 92191; 858-792-9003; 858-792-2743 (fax); tes@cryogel.com (e-mail); www.cryogel.com (website).